It is known to use hydrodemolition to scarify a properly vertical wall using a top down approach as described in U.S. Pat. No. 8,827,373 to MacNeil et al. commonly owned with the present application. MacNeil et al. describe a prior art approach of using cables to suspend a worker platform or a cage from the top of the wall enabling personnel to work the surface of the wall below. MacNeil et al.'s application is directed to providing a horizontally elongated rigid support frame supported from the top of the wall and two spaced rails extending downwardly from a top member. Rigidity between the two rails is provided by a nozzle carriage extending between the two rails and that is adapted to move up and down the rails to work the wall surface.
Inclined or steeply inclined walls present a unique set of problems. The incline of the wall would interfere with a properly suspended top-down system while it may also provide potential support for whatever system is to be used. The tension between avoiding the incline of the wall or relying on it for support arises in the context of the hydrodemolition of the walls of dams and dam spillways.
The hydrodemolition of the steeply inclined walls of dams and spillways is sometimes accomplished using a vehicle that travels along the top of the wall. A boom extends from the vehicle down the surface of the wall while a nozzle assembly at the end of the boom works the surface of the wall. Use of such an arrangement is of course limited to walls that are no taller than the reach of the boom.
It is also known to use a vehicle at the bottom of the wall. The vehicle includes a vertical mast and a carriage travels up and down the mast to work the surface of the wall. An image of such an approach can be found at page 2 of the www.aquajet.se/hydrodemolition_job_20.asp. If the boom is to lean into an inclined wall, articulation of the boom must be provided, as well as ensuring that the vehicle does not tip over due to misalignment of the upwardly extending boom.
For vertically curved dam or spillway walls, it is known to mount a pair of temporary curved rails that are spaced above the surface of the wall and that span the height of the wall, tracking its curvature. The rails are secured to the top and the bottom of the wall. A carriage containing a nozzle assembly extends between the opposed rails and is moved vertically along the wall by means of a winch. See Hydrodemolition and Shotcrete for Rehabilitating a Reservoir Spillway, Shotcrete Magazine, Winter 2013, p. 49.
Another approach is to use a flat working platform extending horizontally across the spillway surface. The entire platform can be moved up and down the inclined dam spillway surface by means of winches. A wheeled mobile hydrodemolition vehicle travels laterally back and forth along the platform to work the surface using an articulated arm that extends from the vehicle to position a nozzle assembly and associated shroud against the wall surface. Such an approach was used on the Guri Hydroelectric Power Station in Venezuela using a mobile robot by Conjet AB.
It is an object of the present invention to provide an effective system for treating a large and steeply inclined surface by hydrodemolition.
That and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows. Note that the objects referred to above are statements of what motivated the invention rather than promises. Not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims.